Re: I-D Action:draft-klensin-rfc2821bis-10.txt

[John C Klensin]

--On Wednesday, 16 April, 2008 14:31 -0600 Willie Gillespie
<[EMAIL PROTECTED]> wrote:

> Tony Finch wrote:
>> On Wed, 16 Apr 2008, Ned Freed wrote:
>>>> I doubt that it makes sense to accept email from
>>>> [EMAIL PROTECTED] on a system that can only
>>>> communicate with IPv4 addresses.
> 
> I foresee some company setting up an IPv6 to IPv4 e-mail relay
> for individuals or other companies that only have IPv6
> addresses.

Very likely, IMO

> For an IPv4-only receiving system, would this appear as an
> e-mail from [EMAIL PROTECTED] (even though it comes over
> the IPv4 link)?  At that point, would it make sense to accept
> the message?

Sure.  The problem arises if the receiving IPv4 host tries to do
some sort of sender-accessibility or callback verification.  It
won't be able to reach the IPv6 host (or send NDNs to it) unless
it either it is configured to submit those messages via an
IPv6-capable gateway or the IPv6 host advertises IPv4 addresses
(perhaps via a conversion relay in a low-preference MX record).

Did I hear you volunteer to organize the I-D leading to a BCP
that I suggested earlier?

    john